The cement industry plays a crucial role in societal development. Every stage of cement production involves the processing and handling of raw materials, inevitably leading to the generation of dust. Ventilation and dust collection systems are among the primary means of preventing dust-related issues in cement plants. If these systems fail, the likelihood of accidents increases, potentially leading to widespread dust problems. By actively adopting scientific and effective dust collection technologies, the cement industry can achieve sustainable, green, and safe development.
1. Sources of Dust in the Cement Industry and Principles of Dust Collection Technology
1.1 Sources of Dust
- Grinding System: The grinding system is responsible for the milling of raw materials and cement. Discrepancies in airflow velocity, grinding fineness, grinding output, and ventilation can result in significant dust emissions. Human error during operations can also contribute to excessive dust.
- Drying Process: During the drying process, rotary kilns operate continuously, causing materials and coal powder to be stirred up and discharged in the airflow from the dryer.
3 Cement Production: The cement production stage, particularly during crushing, generates a substantial amount of dust. Fine particles are also released during material feeding, leading to dust pollution.
1.2 Principles of Dust Collection Technology
The application of dust collection technology in cement plants should be closely integrated with the specific stages of cement production, utilizing scientifically sound methods to minimize dust emissions. Key principles include:
- Reliability of Basic Data: Emphasize the importance of reliable data across the entire cement plant’s operations, ensuring a rational overall layout.
- Energy Efficiency: Focus on continuously reducing energy consumption and preventing secondary pollution, aligning with both the short-term and long-term development goals of the cement plant. Meeting the plant’s production objectives should be a fundamental criterion.
- Selection of Technology: Opt for scientific, advanced, and mature processing methods to enhance the overall effectiveness of dust collection technology, ensuring that it fully meets the needs of cement production and construction.
- Cost Reduction: Strive to lower investment, energy consumption, and operational costs. Simplify and optimize production processes, ensuring safety while meeting emission standards.
- Safety Considerations: Address common safety hazards in cement production by implementing effective protective measures and backup systems.
2. Practical Applications of Dust Collection Technology in the Cement Industry
Effective implementation of dust collection technology in the cement industry requires the selection of high-efficiency dust collectors tailored to specific equipment and operational conditions. Upgrading and optimizing existing dust collectors are also essential to promote green and efficient development within the industry.
2.1 Electrostatic Precipitators (ESP)
Electrostatic precipitators play a crucial role in dust collection within the cement industry. They offer an initial dust collection efficiency of up to 99%, capable of handling large volumes of flue gas. ESPs perform well in high-temperature environments, withstanding temperatures up to 500°C, making them suitable for use at the kiln head to mitigate adverse effects of high temperatures. They operate continuously and automatically with minimal energy consumption by the fan, thus requiring low maintenance costs. However, ESPs have limitations, including large footprint requirements, sensitivity to dust resistivity, potential electrode deformation during long-term use, and the inability to perform offline maintenance. The process involves gas ionization, dust charging, dust deposition, and ash removal. ESPs are particularly effective at the kiln head, where temperatures are higher, and can be optimized by combining them with resistivity control and humidification systems to enhance dust collection efficiency.
2.2 Bag Filter Technology
The application of bag filters in cement plants is also highly effective. Their advantages include exceptionally high dust collection efficiency, which significantly reduces particulate emissions. Bag filters are not adversely affected by variations in inlet dust concentration or dust resistivity and offer stable performance across various load conditions. Maintenance can be carried out without stopping production. However, they have higher operational resistance, greater energy consumption, and filter bags that typically last only 3-4 years, leading to higher operational costs. Bag filters work by using filter media to capture and collect dust from the gas stream, effectively purifying the gas. It is crucial to ensure that the filter media is cleaned regularly to maintain optimal filtration and extend the lifespan of the filter bags. As a dry, high-efficiency dust collector, bag filters are well-suited to meet stringent emission standards, and their application is becoming increasingly widespread. In cement plants, the kiln head typically utilizes oxidation-resistant needle felt materials with cage frames having 16 vertical ribs and fibers capable of withstanding temperatures above 200°C. At the kiln tail, PTFE-coated fiberglass materials are used with cage frames having over 24 vertical ribs, with Teflon stitching to manage operational resistance effectively.
2.3 Dryer Gas Dust Collection Technology
In addition to the above technologies, the drying process also plays a role in dust collection. However, the dust emitted from dryers typically has higher temperature, humidity, and concentration, and most cyclone separators do not meet the environmental standards of the cement industry, posing corrosion risks. To address this, anti-condensation fiberglass dust collection technology can be employed in the drying process to effectively control dust content and enhance the dust collection capability of cement plants.
Conclusion
Practical applications of dust collection technology in the cement industry demonstrate that both electrostatic precipitators and bag filters achieve excellent dust collection results. They offer high dust collection efficiency with comparable economic costs. However, bag filters provide a more optimized solution for reducing dust emissions, maintaining stable operations, and meeting low emission requirements. Compared to these two technologies, the dust collection methods for dryers are less effective. Overall, in the future development of the cement industry, the active use of bag filters can fully leverage their advantages and contribute to effective dust management.
