A cement classifier or cement mill separator is a key equipment in a closed-circuit cement grinding plant. It was created to improve the grinding efficiency in a cement plant and increase output per hour while lowering the production energy. Today we are going to see the application and value of cement classifiers in cement plants and find out how cement separators help optimize efficiency. Before looking into real cases, let’s first know some basic information about cement separators.
Why use a cement classifier?
In the process of cement industry development, factories are facing many challenges such as particle size control, high energy consumption, and more and more strict environmental rules.
Particle size control problem:
Over-size particles or over-grinding fine particles will affect the final property of the cement in aspects such as strength and setting time.
High energy consumption problem:
The high energy consumption in the cement industry is an essential problem. However, the cement classifier can contribute to energy saving.
Environmental problem:
Facing more and more restrictive emission requirements, how to reduce dust and particulate matter emissions is one key challenge to cement plants.
Separator in cement mills plays a crucial role in improving separation efficiency, and optimizing the distribution of particles and in turn highly affect productivity and energy. It selects qualified particles out from coarse ones which are sent back to the mills for regrinding. Doing so can prevent fine particles from adhering to the mill where buffer may arise so that the grinding efficiency is improved. Also, it can adjust the combination of particles to avoid uneven fine particles. As a result, the grinding quality is guaranteed and the output per unit time is increased. It is calculated that under the same conditions, the output of a closed-circuit mill is 50%~100% higher than that of an open-circuit mill.
How does an o sepa separator work?
The cement classifier utilizes physical forces to separate fine particles from coarse particles. Take the most advanced o sepa separator for example, particles of different sizes are separated by air current and centrifugal force. Feed materials fall into the separation zone by a spreader plate on top, and a horizontal vortex generated by the rotating cage in the center provides air current and centrifugal force to absorb and collect fine particles while the coarse particles drop off due to gravity. The fineness of particles can be adjusted by changing the speed of the rotor and the air volume of the circulation fan.
Case study: Nu high-efficiency separator in upgradation of vertical raw mill
As now we have briefly understood the working principle of cement classifiers, it is time to come to a real case and get a clear picture of how important the role a cement classifier plays in a cement plant.
Background
A cement plant adopts a vertical roller mill output of 500t/h for raw mill grinding.
Problems
High energy consumption is caused by high system resistance, high-pressure difference of mill, large air leakage, low efficiency of cement separator, and low efficiency of circulating fan.
Solutions
The cement plant has made changes in many aspects, while we only focus on the change of the cement separator. A new type low resistance high-efficiency cement classifier substitutes the old one. However, the structure of the former separator has remained which can reduce costs. To be specific, the drive system, air outlet, electromotor, and reducer are kept. The rotor, blades, shell, lower part cone, and feed pipe are replaced.
The core technique for this cement classifier is the U-shape moving blades. Compared with the common direct blade of the separator, it can reduce the resistance by 30%, improve separation efficiency by 9.13%, and reduce cyclic load rate by 312%, under the same working conditions. Besides, the particle size distribution of the finished product can be effectively controlled by adjusting the angle of the external wind wing.
Another important technique is the air regulation applied on the middle shell. It is based on the principle of reducing air volume for the grinding mill to fulfill the demanding air volume for the cement separator. The air circulation is reduced as much as possible, and the air volume for the cement classifier is unchanged to realize the reduction of air circulating resistance on one side while reducing the coarse particles entering the cement classifier. The separation efficiency is improved and the fine particles are less likely to turn back to the mill. Also, the stability of the material layer and the grinding efficiency are improved, and the power consumption is reduced.
Results
After over two years of practice, the power consumption of the cement raw meal drops year by year. 27.1% power is reduced after modification which saves a lot of costs. Below is a simple table for the energy consumption statistics from 2017 to 2020.
| 2017 | 2018 | 2019 | 2020 first half year | 2020 to 2017 | Comprehensive clinker power consumption |
| 17.05 kW/h | 15.73 kW/h | 15.19 kW/h | 12.43 kW/h | -4.62 kWh/t | -7.23 kWh/t |
Summarize
Choose a suitable cement classifier
Choose a cement classifier that best suits the requirements of the cement plant based on productivity, product type, and energy costs.
Integration with cement mills
The integration of cement classifiers with cement mills (cement ball mills, vertical roller mills, etc.) is important. Closed circuit grinding systems can significantly improve the overall grinding efficiency and the final product quality.
Regular maintenaince and inteligient monitor
By using the Intelligent monitor system, cement classifiers can get real-time monitoring and predictive maintenance reduce downtime, and prolong equipment service life.
Environmental protection and energy efficiency combination
By using a highly efficient filter system and wear-resistant material, the cement separator can not only improve production efficiency but also help reduce dust release to meet environmental standards.
Conclusion
The air classifier plays a vital role in the cement industry. It significantly improves production efficiency through precise particle size control and reduces excessive grinding of materials, thereby effectively reducing energy consumption. In addition, air classifiers can improve the quality of cement products and ensure uniform particle size distribution while significantly reducing dust emissions to meet increasingly stringent environmental requirements. Facing future production and environmental protection challenges, companies in the industry should actively pay attention to and invest in the innovation and upgrading of cement classifier technology to achieve a more efficient and sustainable production model.
