At present, the cement industry is facing a very severe situation, and energy saving and carbon reduction has become the key task for enterprises to achieve sustainable development. For cement enterprises, it is urgent to explore the transformation direction and specific measures to achieve energy saving and carbon reduction in production lines at a small cost. In this regard, China Cement Network interviewed Qi Yanyong, an associate professor of Southwest University of Science and Technology, focusing on the two key links of decomposition furnace and rotary kiln, and deeply analyzed the feasible path of energy saving and carbon reduction.
1. Energy-saving and carbon-reducing transformation
of precalciner (1) Analysis of
current situation At present, the decomposition rate of raw materials entering the kiln of precalciner kiln system can mostly reach 93%. The outlet temperature of the decomposition furnace is actually controlled in the range of 860-880 ℃, and there are O O and CO at the outlet. This phenomenon leads to the high temperature of the exhaust gas from the primary cylinder. From the theoretical calculation and practical production optimization and transformation practice, in the existing cement precalciner kiln process, if the outlet temperature of the precalciner is controlled at 850 ℃, it is enough to ensure the complete decomposition of calcium carbonate. Moreover, for the high efficiency calciner, the exhaust gas temperature of the first stage cylinder corresponding to the five-stage preheater should be lower than 300 ℃, and that of the six-stage preheater should be lower than 240 ℃.
(2) Reasons
for the low efficiency of the calciner 1. The trajectory of raw meal and pulverized coal in the calciner lacks clear and definite characterization, which makes it difficult to control the production process accurately.
2. Pulverized coal wrapped by raw meal occurs from time to time, which slows down the combustion rate of pulverized coal and increases the low temperature (lower than decomposition temperature of carbonate) area.
3. The design of the cone part of the calciner is unreasonable, and the working state of the spreader box is not good, which makes the raw material with low decomposition rate enter the rotary kiln and affects the subsequent production.
4. The operating parameters are unreasonable, the opening of the tertiary air damper is too large, and the necking air speed of the smoke chamber is too low, which are not conducive to the efficient operation of the decomposition furnace.
(III) Optimization measures
1. Use the spreader box with adjustable spreader plate angle to optimize the distribution of raw materials in the decomposition furnace and improve the decomposition efficiency.
2. Optimize and adjust the position and angle of the tailings into the calciner to ensure that the pulverized coal can be fully burned and improve the energy utilization rate.
3. Optimize the design of the tertiary air inlet of the decomposition furnace to improve the air inlet condition and promote the reaction in the furnace to be more sufficient.
2. The heat transfer efficiency of the rotary kiln is improved, the thermal system is stable and the heat transfer capacity of the
rotary kiln is proportional to the flame temperature and the fourth air. Concentrated and rapid combustion of pulverized coal is the best way to increase the temperature of the firing zone and the most effective way to reduce coal consumption. Stable thermal system is an inevitable requirement to reduce energy consumption. It is a feasible way to realize the efficient operation of rotary kiln by intelligent identification of the working conditions of kiln and grate cooler, real-time monitoring and adjustment of relevant parameters.
(I) Adjust combustion conditions
1. Fuel stability: strictly control the fineness of pulverized coal at 1% -3% (80 micron sieve residue) to ensure stable fuel quality and lay the foundation for efficient combustion.
2. Air volume control of the rotary kiln: ensure that there is enough excess air to make the oxygen content in the smoke chamber not less than 3%, so as to promote the full combustion of the fuel.
3. Selection of burner: select the burner with high air pressure (external air pressure greater than 60 kPa) and low air volume to improve the combustion efficiency.
4. Oxygen-enriched combustion: Oxygen-enriched air with a concentration of not less than 35% is used inside and outside the burner to enhance the combustion effect.
(2) Intelligent control
uses big data to deeply analyze the relationship between negative pressure and ventilation rate of rotary kiln decomposition furnace, explore the relationship between kiln current and material movement, heat transfer and chemical reaction of rotary kiln, and accurately identify the gas-solid heat exchange condition of grate cooler. By establishing a comprehensive model of combustion, heat transfer and gas movement in the kiln system, the problems existing in the kiln system are analyzed on line, so as to stabilize the thermal system and move towards the goal of unattended intelligent control.
In the current severe situation of the cement industry, enterprises can significantly improve the energy efficiency of the production line, reduce carbon emissions, enhance the competitiveness of enterprises in the market, and contribute to the green and sustainable development of the cement industry by implementing the above energy-saving and carbon-reducing transformation measures for the decomposition furnace and rotary kiln at a lower cost. On March 13-14,
2025, China Cement Network will hold the 14th China Cement Industry Summit and TOP100 Award Ceremony in Hangzhou . At the same time, the "50 People Forum on Cement Economy" was held . This summit will bring together industry elites and multi-resources to discuss and deal with the difficulties faced by the industry from the perspectives of optimal allocation of supply side, precise docking of demand side, deep insight into macro-economy and frontier promotion of technological innovation, and jointly create a new chapter for the industry! At the meeting, Qi Yanyong will bring a wonderful report. Hurry up to sign up!
