At present, the situation of cement industry is grim, and energy saving and carbon reduction has become the core proposition for cement enterprises to seek sustainable development. In the case of cost constraints, how to achieve energy-saving and carbon reduction transformation of production line with lower investment is an urgent problem for every cement enterprise to solve, and it is urgent to explore specific transformation direction and effective measures.
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.
Faced with the severe situation of the cement industry, if enterprises can implement energy-saving and carbon reduction transformation schemes for precalciners and rotary kilns, they can greatly optimize the energy efficiency of production lines and effectively reduce carbon emissions without high investment, which will not only help to enhance the market competitive advantage of enterprises, but also inject important momentum into the cement industry towards the goal of green and low-carbon development.
In order to accelerate the realization of the "double carbon target" and actively promote the green and high-quality development of the industry, China Cement Network will hold the "2025 China Cement Double Carbon Conference and the 13th Energy Conservation and Environmental Protection Technology Exchange Conference" on May 27-28, 2025. At the same time, the release ceremony of "2025 ESG Ranking List of Cement Industry" was held . This conference will bring together industry elites and multi-resources to provide all-round support for the industry in terms of technology, policy landing and resource docking. At the meeting, Qi Yanyong will bring a wonderful report. Hurry up to sign up!
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